j0245851

 

These lecture notes are the exclusive property of Red Wagon Tutorials.  They may not be used except by a student who has paid a fee for access.  The notes that follow, the video recording, and all supporting materials are copyrighted and may not be reproduced without specific written permission from the course instructor or Red Wagon Tutorials.

 

For those of you who do not want to listen to the information at the beginning of each class given to my students and who only want to listen to the recorded lecture, I post a lecture starting point in minutes and seconds on every (w) version of the notes. The MP4 Player allows you to fast forward to this starting point. The material at the start of each class recording gives excellent scheduling, test review, and lab report construction information.

To fast forward the MP4 download, pause the recording, allow the recording to load past the start point, then resume the playback from that point. It may take three to four minutes (or longer) depending on the speed of your internet connection for the recording to download to the starting point.

Lecture Starts: 20:50

 

Thermodynamics, Part 1

 

Lecture: CModule13-1w

 

http://redwagontutorials.com/HandoutsC/Module13/1stOverhead25.htm

 

http://rwt.apologia.com/   (Test Review)

 

http://redwagontutorials.com/HandoutsC/Module13/ExperimentGrade2.htm

 

http://redwagontutorials.com/HandoutsC/Module13/FormalReport2d.htm

 

http://www.kentchemistry.com/links/Matter/EndoExo.htm

 

1.  When solutes dissolve exothermically, they release what, which causes the solution to heat up?   _______________

 

When solutes dissolve exothermically, they release energy, which causes the solution to heat up.

 

http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA3/MAIN/THERMIT/PAGE1.HTM 

 

2.  When a solution cools down after the solute and solvent are mixed, the process is said to be _______________, which indicates that energy is being absorbed from the surroundings.

 

When a solution cools down after the solute and solvent are mixed, the process is said to be endothermic, which indicates that energy is being absorbed from the surroundings.

 

http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA3/MAIN/ENDO2/PAGE1.HTM

 

3.  T or F:  When a solute dissolves in a solvent, no chemical change occurred.   ________

 

True:  When a solute dissolves in a solvent, no chemical change occurred.  When things dissolve, they undergo a physical change only.

 

http://www.ps.uci.edu/~tomba/ants/sugar.jpg

 

4.  If a chemical reaction is exothermic, energy is which of the following in the reaction?

 

a.  a product

b.  a reactant

c.  a bystander

d.  a warm Spring day

 

If a chemical reaction is exothermic, energy is a product in the equation.  If the chemical reaction is endothermic, energy can be considered a reactant in the chemical equation.

 

http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA3/MAIN/VOLCANO/PAGE1.HTM

 

5.  Energy is never really _______________ nor _______________ by a chemical reaction.

 

According to the First Law of Thermodynamics, energy is never really produced nor consumed by a chemical reaction.  It can only change forms.

 

http://apod.nasa.gov/apod/image/0511/sunflame_soho_big.jpg

 

6.  If the chemical reaction is exothermic, the entire reaction will get what?   _______________

 

If the chemical reaction is exothermic, the entire reaction will get hot.

 

http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA3/MAIN/NACL/PAGE1.HTM  

 

7.  T or F:  According to Dr. Wile, there are two types of energy: electric and gas.   ________

 

False:  According to Dr. Wile, there are two types of energy: potential and kinetic.

 

http://www.physicsclassroom.com/mmedia/energy/se.cfm

 

8.  Potential energy is defined as which of the following?

 

a.  stored energy

b.  motion energy

c.  canned energy

b.  bottled energy

 

Potential energy is defined as stored energy.  Energy stored in the chemical bonds of a substance is potential energy.

 

http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA3/MAIN/CLACET/PAGE1.HTM   

 

9.  From a chemistry point of view, heat energy associated with a chemical reaction is considered _______________ energy.

 

Kinetic energy is defined as energy in motion.  From a chemistry point of view, heat energy associated with a chemical reaction is considered kinetic energy.

 

10.  If a chemical reaction is exothermic, some of the potential energy stored in the reactants is converted into what?   _______________  _______________

 

If a chemical reaction is exothermic, some of the potential energy stored in the reactants is converted into kinetic energy.

 

http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA3/MAIN/NITRO3I/PAGE1.HTM

 

11.  T or F:  If a chemical reaction is endothermic, kinetic energy from the surroundings is converted into potential energy stored in the products’ chemical bonds.   ________

 

True:  If a chemical reaction is endothermic, kinetic energy from the surroundings is converted into potential energy stored in the reaction products’ chemical bonds.

 

12.  If the chemical reaction is endothermic, the entire reaction will demonstrate which of the following?

 

a.  colder temperature

b.  higher pressure

c.  greater volume

d.  no change what so ever

 

If the chemical reaction is endothermic, the entire reaction will get colder.

 

http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA3/MAIN/ENDO2/PAGE1.HTM

 

13.  Exothermic reactions have energy as a _______________ and endothermic reactions have energy as a _______________.

 

Exothermic reactions have energy as a product and endothermic reactions have energy as a reactant.

 

14.  T or F:  The reaction, HCl + NaOH à H2O + NaCl + energy, indicates an exothermic reaction.   ________

 

True:  The reaction, HCl + NaOH à H2O + NaCl + energy, indicates an exothermic reaction.

 

http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA3/MAIN/SH2OICE/PAGE1.HTM 

 

15.  What is the potential energy stored in a substance called?   _______________

 

Enthalpy is the potential energy stored in a substance.

 

http://www.ausetute.com.au/enthchan.html

 

16.  The change in enthalpy is indicated by which of the following? 

 

a.  ΔA

b.  ΔB

c.  ΔH

d.  ΔZ

 

The change in enthalpy (ΔH) is the energy change that accompanies a chemical reaction.

 

17.  The units attached to ΔH are either _______________ (kJ) or _______________ (kcal).

 

The units attached to ΔH are either kiloJoules (kJ) or kilocalories (kcal).

 

18.  The value of ΔH depends on the what of reactants undergoing the chemical change?   _______________

 

The value of ΔH depends on the amount of reactants undergoing the chemical change.

 

http://www.shodor.org/UNChem/advanced/thermo/index.html 

 

19.  T or F:  A ΔH of 50 kJ/mole means that 50 kJ of energy change occurred from one mole of product consumed.   ________   

 

False:  A ΔH of 50 kJ/mole means that 50 kJ of energy change occurred from one mole of reactant consumed.

 

20.  ΔH for all endothermic reactions is which of the following?

 

a.  positive

b.  negative

c.  a mythical value with can’t be determined

d.  playing quarterback for the Seattle Seahawks

 

http://www.wolverinefireworks.com/videos/wp-content/uploads/SeattleSeahawks.jpg    

 

ΔH is positive for endothermic reactions, and ΔH is negative for exothermic reactions.

 

21.  Write a balanced chemical equation for the reaction between H2CO3 and KOH.  The enthalpy for the reaction is -21 kcals.  Include the given energy in the equation.

 

______________________________________________________

 

http://redwagontutorials.com/HandoutsC/Module01/BlankPage.htm

 

H2CO3 is an acid and KOH is a base.  This is an acid/base reaction that produces salt and water:

 

H2CO3 + KOH à H2O + K2CO3

 

Balance the equation.  The reaction has a negative enthalpy and releases energy.  Add the energy as a product:

 

H2CO3 + 2KOH à 2H2O + K2CO3 + 21 kcals

 

22.  How many ways are there for determining the ΔH in a chemical reaction?   ________

 

There are three ways of determining the ΔH in a chemical reaction: calorimetry, bond energies, and Hess’s Law.

 

http://us.mt.com/etc/medialib/mt_ext_files/Product/Product/4/HPDSC827_HP_DSC_0x0002494700025420000753f9_files.Par.HP_DSC_l_jpg.Image.jpeg

 

http://www.chemistryland.com/CHM130W/11-Bonds/bondEnergies.jpg

 

http://www.uwplatt.edu/~sundin/114/l114a45.htm

 

23.  In Experiment 13.1, Determining ΔH of a Chemical Reaction, the lye and acetic acid reacted to form _______________ and _______________.

 

In Experiment 13.1, Determining ΔH of a Chemical Reaction, the lye and acetic acid reacted to form water and salt.  It is a standard acid/base reaction that produces heat.

 

http://redwagontutorials.com/HandoutsC/Module13/Experiment13.1.htm

 

Remember: there are example calculations in the solutions manual.

 

24.  T or F:  When a chemical reaction occurs, the valence electrons of the atoms that make up the products must rearrange themselves into the configurations necessary to make the reactants.   ________

 

False:  When a chemical reaction occurs, the valence electrons of the atoms that make up the reactants must rearrange themselves into the configurations necessary to make the products.

 

http://cmapsnasacmex.ihmc.us/rid=1162340909128_827667331_35171/45%20CovalentBond.cmap?rid=1162340909128_827667331_35171&partName=htmljpeg

 

25.  When octane burns the following reaction occurs:

 

2C8H18 (l) + 25 O2 (g) à 16 CO2 (g) +18H2O (l)

 

To make this happen, all the bonds on which side of the reaction must be broken?

 

a.  the reactant side

b.  the product side

c.  the blind side

d.  the dark side  (Luke, come on over?)

 

To make this happen, all the bonds on reactant side of the reaction must be broken.

 

http://upload.wikimedia.org/wikipedia/commons/thumb/0/0f/Gas_Station_Pump_Five_Octane_Ratings.jpg/687px-Gas_Station_Pump_Five_Octane_Ratings.jpg

 

26.  To break the bonds of the octane and oxygen, what must be absorbed?   _______________  

 

To break the bonds of the octane and oxygen, energy must be absorbed.  When product bonds are formed, energy is released.

 

27.  If reactant bonds are strong and product bonds weak, the reaction will be _______________.

 

If reactant bonds are strong and product bonds weak, the reaction will be endothermic.  More energy will be required to break the bonds than energy produced by forming those bonds.

 

If reactant bonds are weak and product bonds strong, the reaction will be exothermic.  Less energy will be required to break the bonds than energy produced by forming those bonds.

 

28.  T or F:  The difference between exothermic and endothermic reactions depends on how much energy is absorbed and how much energy is released.   ________

 

True:  The difference between exothermic and endothermic reactions depends on how much energy is absorbed and how much energy is released.

 

http://web.stteresa.edu.hk/~kfyuen/s6ch602.jpg

 

29.  The measured strength of a chemical bond is which of the following?

 

a.  007

b.  Schwarzenbond

c.  Krazy Glue

d.  bond energy

 

Bond energy is the measured strength of a chemical bond.

 

http://en.wikipedia.org/wiki/Chemical_bond

 

30.  Both bond energy and ΔH are measured in what units?   _______________

 

Both bond energy and ΔH are measured in what kJ/mole.  (Note: This is the primary way they are shown.  They could also be measured in kcal/mole or any energy unit.)

 

http://redwagontutorials.com/HandoutsC/Module13/Table13.1.htm

 

31.  Bond energies relate the amount of energy required to break one mole of the bonds and also relates the amount of energy required to _______________ one mole of these bonds.

 

Bond energies relate the amount of energy required to break one mole of the bonds and also relates the amount of energy required to form one mole of these bonds.

 

32.  T or F:  ΔH = Energy required to break bonds + Energy released when bonds form.   ________

 

False:  ΔH = Energy required to break bonds – Energy released when bonds form.  ΔH will be positive if the energy necessary to break the bonds is greater than the energy released.  ΔH will be negative if the energy release is greater than the energy necessary to break the bonds.

 

http://www.saskschools.ca/curr_content/chem30_05/1_energy/energy2_6.htm

 

33.  In an acetylene torch, C2H2 is burned to make the hot, blue flame that cuts or welds metal. Assuming that the combustion is complete, what is the ΔH of this reaction?

 

____________________

 

http://redwagontutorials.com/HandoutsC/Module13/Table13.1.htm

 

The unbalanced equation would be:

C2H2 + O2 à CO2 + H2O

 

The balanced equation would be:

 

2C2H2 + 5O2 à 4CO2 + 2H2O

Lewis structures of the chemicals involved:

 

eh, louie!

 

Calculate the bond energies broken and bond energies produced:

(1)  two moles of triple C-C bonds broken x 835 kJ/mole = 1670 kJ/mole

(2)  four moles of single C-H bonds broken x 411 kJ/mole = 1644 kJ/mole

(3) five moles of double O=O bonds broken x 494 kJ/mole = 2470 kJ/mole

Total broken = 5784 kJ/mole

(4) eight moles of double C=O bonds made x 799 kJ/mole = 6392

(5) four moles of single H-O bonds made x 459 kJ/moles = 1836

Total made = 8228 kJ/mole


The ΔH for this reaction, then, is -2,444 kJ, and it is exothermic

 

34.  Whose Law can be stated as, “Enthalpy is a state function and is, therefore, independent of its path.”

 

a.  Boyle’s

b.  Chuck’s

c.  Hess’s

d.  Wile’s

 

Hess’s Law can be stated as, “Enthalpy is a state function and is therefore independent of its path.”

 

http://en.wikipedia.org/wiki/Germain_Henri_Hess 

 

35.  T or F:  2 + 2 = 4 and 10 - 6 = 4.  “4” in this case could be considered a state function.   ________

 

True.  A state function is any quantity that depends solely on the final destination (the number 4), not on the way one gets to that destination (2 + 2 or 10 - 6).

 

http://itl.chem.ufl.edu/2045_s00/lectures/lec_7.html

 

36.  ΔHfo indicates the enthalpy of formation, which is measured at ________ oC and ________ atm.

 

ΔHfo indicates the enthalpy of formation, which is measured at 25 oC and 1.00 atm.

 

http://redwagontutorials.com/HandoutsC/Module13/Table13.2.htm

 

http://en.wikipedia.org/wiki/Standard_enthalpy_change_of_formation

 

37.  The standard enthalpy of formation of an element in its elemental form is what?   _______________

 

The standard enthalpy of formation of an element in its elemental form is zero.

 

http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA3/CONTENTS.HTM